Added amp...getting some transients...I think

[plincoln]

First off, here is the equipment I am using...

Pioneer 1014 AVR
HK Citation 5.1 Amp


Up until now, I have been using the pioneers internal amps for powering my 7 channels. I decided to offload the front three onto a separate amp using the Pioneers Pre-outs...well I am getting a pop anytime the amp is connected to the pre-outs and the pioneer is changing inputs or audio signals (drop down to stereo from DD, etc).

Strange thing is, it will make the speakers pop, even if the speakers are not connected to the HK amp...what I mean is, if I leave the speakers attached to the pioneer high level outputs and connect the HK Amp to the pre-outs and then change signals, the speakers whose pre-outs are connected to the amp will pop even though the speakers are not physically attached to the outputs of the HK. Hopefully that makes sense...I had this problem with an adcom amp as well...

I thought it could be that the pioneer was discharging some DC across the pre-outs, but the HK has dc protection on the outputs..and since the speakers are not attached to the outputs of the HK, that doesn't seem to make sense. yet when I place a cap between the pioneer and the HK amp, this popping goes away.

Any ideas for a remedy? I'd hate to not use the HK since it would become a boat anchor otherwise...

thanks
-patrick

[JonMarsh]

You've got low level DC offset in the system, allright- the pop comes from the small current surge to charge or discharge- may also be input bias/leakage current from the HK BACK into the Pioneer- only way to know to know for sure would be to scope it.

It's not unusual for there to be small offset voltages in the outputs of line stages, especially if they're not operated with a servo. You HK is probably direct coupled, which is why adding the cap makes that more or less go away.

[plincoln]

You've got low level DC offset in the system, allright- the pop comes from the small current surge to charge or discharge- may also be input bias/leakage current from the HK BACK into the Pioneer- only way to know to know for sure would be to scope it.

It's not unusual for there to be small offset voltages in the outputs of line stages, especially if they're not operated with a servo. You HK is probably direct coupled, which is why adding the cap makes that more or less go away.

Thanks for response Jon, that's what I suspected. Any quick fix to decoupling the HK without detrimentally affecting the FR of the mains? I'd almost prefer if it was something I could mod inside the HK to keep it clean...but at this point I'd do almost anything to get rid of the pop.

Edit: I've got access to scope etc...I just need to know what and how I need to measure to verify this.

[Amphiprion]

Probe the RCA hot and ground on the pre-out with it set to trigger on basically anything over, shucks, i dunno. Some small value. Then change the signal source on the receiver (if I am understanding the problem correctly).